Some of prior art thermal printers are configured to print and erase letters, using printing and erasing common-use ribbon interposed between printing paper and a head, as disclosed in U.S. Pat. No. 4,384,797.
However, since there has been no idea to print a letter, reusing a portion of the ink ribbon once used to erase an erroneous letter, different portions of the ink ribbon must be used for printing operation and erasing operation. This apparently accelerates consumption of ink ribbon, and frequent exchange of ink ribbon cassettes increases the running cost of the word processor or typewriter.
Additionally, the prior art thermal printer requires a movable ribbon guide to change the timing for stripping the ribbon from the paper between printing operation and erasing operation, and this invites a complicated structure of the printer.